Deprecate First and Last in Data.Monoid

[Henning Thielemann]

On Wed, 11 Apr 2018, Andrew Martin wrote:

> (As an aside, and the confusion I’m talking about here isn’t entirely 
> hypothetical. I got tripped up by this when I first started using the 
> semigroups library. I had to train myself to stop importing Data.Monoid 
> unqualified, because it kept stealing these identifiers)

Unqualified imports are not the problem - unqualified imports without 
import list are the problem. People should not do that.